The officer who fatally shot Hofstra University student Andrea Rebello on Friday is "inconsolable," sources say. The officer responded to the call of a home invasion, and the man charged with the break-in used Rebello as a human shield; one of the officer's shots hit Rebello in the head, killing her instantly.

"He blames himself and keeps replaying it in his mind," a police source told The New York Post. "He is torn up about the poor girl."

Officer Nikolas Budimlic, 42, is currently on sick leave and spending time with his family, including his two young children, while he copes with the shooting. The incident happened on Friday, when Dalton Smith broke into Rebello's home. He took her hostage along with other people in the home; Smith allowed Shannon Thomas to leave with the expectation that she would get him money from a nearby ATM.

Thomas left and immediately called 911 to report that Smith was holding a gun to her friends' heads. Police, including Budimlic, responded to the call and, as Jessica Rebello was running through the front door, entered the home. Budimlic was separated from his partner and trapped inside with Smith, Andrea, and another hostage, who then yelled that the police were in the home.

"The officer lost the element of surprise," a source said.

Smith took advantage of the moment and grabbed Andrea and used her as a human shield. As he raised his gun, Budimlic raised his and fired off eight shots, one of which hit Andrea in the head.

"The officer eventually fired eight rounds in total. Seven of those rounds struck our subject, one of those rounds struck the victim," Detective Lt. John Azzata told ABC News.

"It was a tragic accident. There's no reason to believe that any protocol was not followed. There's no playbook. You arrive at a home, and the guy has a gun to the victim's head – what do you do? You rely on your training and your instincts and hope for the best outcome," a police source told The Post.

Rebello's classmates held a moment of silence and wore white ribbons for their fallen colleague at graduation this weekend. Her funeral will be held on Wednesday in Sleepy Hollow, New York.